Epoxy materials have a high crosslinking density, which provides them with a high glass transition temperature Tg, which confers excellent thermomechanical properties on the material. The higher the crosslinking density, the higher the Tg of the material and consequently the better the thermomechanical properties: the higher the operating temperature limit of the material. Nevertheless, the impact strength properties of epoxy materials are insufficient for numerous applications. Numerous solutions have been developed to attempt to respond to this problem. At the same time, while all epoxy materials are difficult to strengthen with regard to impacts, epoxy materials with high Tg values are the most difficult.
US patent application 2003/0187138 describes a toughener for thermosetting resins which comprised a trithiocarbonate polymer.
The patent EP 0 659 833 describes a composition based on epoxy resins, impact modifier and a mixture of amine hardeners being formed of dicyandiamide, cycloaliphatic amine and polyoxyalkylenamine.
U.S. Pat. No. 486,256 describes a two-part composition comprising an epoxy resin, a chain extender, a base catalyst and a polymeric toughener, especially a core-shell graft copolymer. US Publication US 2003/0187154 describes impact-resistant epoxy resin compositions containing an epoxy resin (A), a copolymer (B), for example a CTBN rubber, a latent hardener (C) and reaction products containing more than one carboxyl group per molecule.
Recently, it has been found that the addition of triblock copolymers having at least one block predominantly composed of methyl methacrylate units to epoxy compositions results in epoxy materials with improved impact resistance; EP1290088.
The patent application WO 03/063572 describes thermoset materials with improved impact strength, obtained from compositions comprising a hardenable resin, typically epoxy resin, polyamide resulting from the condensation of at least one diacid and at least one diamine, and possibly an impact modifier selected from SBM, BM and MBM copolymers.